Concentrating device for high-salt organic wastewater by down-flow double-effect evaporation

Abstract

The application discloses a down-flow double-effect evaporation concentration device for high-salt organic wastewater, which comprises a wastewater conveying pump, a wastewater heater, a flash tank, a circulating mother liquor storage tank, a circulating mother liquor conveying pump, a circulating mother liquor first-stage preheater, a circulating mother liquor second-stage preheater, an evaporation tower and a water cooling tower; concentrated liquid generated in the flash tank is discharged from the bottom and is conveyed together with wastewater collected by a wastewater pipeline via the wastewater conveying pump, and the mixed wastewater conveyed by the wastewater conveying pump is divided into two streams, one of which enters the circulating mother liquor storage tank to supplement the evaporation capacity of the subsequent evaporation process. The vacuum double-effect evaporator in the traditional down-flow double-effect evaporation is replaced by a heat-mass simultaneous evaporation tower which can operate efficiently under normal pressure, so that the vacuum system is avoided, the material requirement and working condition requirement of the equipment are reduced, and the application range and application field of the double-effect evaporation are expanded.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of energy saving and environmental protection and chemical separation technology, and particularly relates to a downstream double-effect evaporation concentration device for high-salt wastewater containing organic matters generated in the production process of chemical industry, pharmaceutical industry and food industry. BACKGROUND

[0002] In the prior art, high-salt wastewater generally refers to wastewater containing salt with a mass concentration of 1% or more. The high-salt wastewater generated in the production process of the chemical industry, the pharmaceutical industry and the food industry usually also contains organic matters such as toluene and DMF due to the process. The generation of high-salt wastewater in industrial activities is inevitable, the generation channels are increasingly extensive, the total amount is expanding year by year, and the impact on the ecological environment is intensifying.

[0003] In the early stage of industry, high-salt wastewater was mainly treated by using high-efficiency salt-tolerant bacteria and diluting and discharging water. However, this treatment method not only wastes a large amount of water resources, but also cannot control the salt discharge from the total amount. In order to better solve the problem of high-salt wastewater, the evaporation process and the crystallization process are used in industry to comprehensively treat the high-salt wastewater generated in industrial production activities.

[0004] The evaporation process can be further divided into single-effect evaporation, multi-effect evaporation, rising film evaporation, falling film evaporation and the like; and the crystallization process can be further divided into concentration crystallization, cooling crystallization, isoelectric point crystallization and the like. Among the above-mentioned evaporation processes, the multi-effect evaporation process wins the favor of most factories due to its advantages of large operation flexibility and low power consumption.

[0005] The multi-effect evaporation process is simply to use the steam generated by the previous evaporator as the heat source of the next evaporator. In the process, each evaporator constitutes one effect of evaporation. In this way, several evaporators are connected in series to cooperatively complete the evaporation task, which is accordingly called several-effect evaporation.

[0006] When naming each evaporator, the corresponding effect number is added before the evaporator to distinguish it. Correspondingly, the steam generated by several-effect evaporators is called several-effect steam or secondary steam generated by the evaporator. The double-effect evaporation is as its name suggests, which is to use two evaporators connected in series to cooperatively complete the evaporation task. It is the most common form of multi-effect evaporation process in factories. It has been used by small and medium-sized factories to date due to its simple process and single equipment. However, in recent years, the simple process of the traditional downstream double-effect evaporation cannot cover up its shortcomings such as serious flow heat loss, high operating cost and the need to maintain the two-effect evaporator in a vacuum state.

[0007] Therefore, in order to solve the above problems, it is extremely urgent to actively improve the original downstream double-effect evaporation process, continue the past and seek a high-efficiency process with mild working conditions and low system heat integration energy consumption.

[0008] Therefore, in order to solve the above problems, it is necessary to develop a double-effect evaporation device which can reasonably recycle the last-effect steam heat and does not need to maintain vacuum condition at all times. SUMMARY

[0009] The present application aims at solving the problems existing in the prior art, and provides a down-flow double-effect evaporation concentration device for high-salt organic wastewater.

[0010] The down-flow double-effect evaporation concentration device for high-salt organic wastewater comprises a wastewater delivery pump, a wastewater heater, a flash tank, a circulating mother liquor storage tank, a circulating mother liquor delivery pump, a circulating mother liquor primary preheater, a circulating mother liquor secondary preheater, an evaporation tower and a water cooling tower.

[0011] The concentrated liquid generated in the flash tank is discharged from the bottom and transported together with the wastewater collected by the wastewater pipeline through the wastewater delivery pump, and the mixed wastewater transported by the wastewater delivery pump is divided into two streams, one of which enters the circulating mother liquor storage tank to supplement the evaporation amount of the subsequent evaporation process.

[0012] The other stream of wastewater is correspondingly sent into the wastewater heater for heating, and the wastewater heated to the preset temperature is continuously sent into the flash tank, the top of the flash tank generates primary steam, the primary steam is sent into the circulating mother liquor secondary preheater as the heat source of the preheater, and after heat exchange and condensation in the preheater, the purified water is discharged and sent to sewage treatment.

[0013] The circulating mother liquor delivery pump draws a stream of circulating mother liquor from the circulating mother liquor storage tank and sequentially sends it into the circulating mother liquor primary preheater and the circulating mother liquor secondary preheater for temperature rise, and after being heated to the preset temperature, the circulating mother liquor is sent into the evaporation tower for spraying; and the mixed gas generated in the evaporation tower is correspondingly sent into the water cooling tower for cooling treatment, and the water vapor in the mixed gas is correspondingly condensed.

[0014] Further, a circulating water delivery pump and a circulating water cooler are further included; the condensed hot water stored in the water cooling tower overflows and is sent into the circulating mother liquor primary preheater as the heat source for heat exchange through the circulating water delivery pump, and the circulating water after heat exchange is divided into three streams, one of which is sent into the water cooling tower for recycling after being cooled to the preset temperature in the circulating water cooler; one is directly sent back to the water cooling tower to maintain the temperature of the tower kettle; and the last one is sent to sewage treatment as purified water.

[0015] Further, the wastewater heater heats the wastewater entering its interior through the low-pressure steam sent in, and the steam condensate is discharged after heating.

[0016] Further, the circulating mother liquor storage tank is further provided with a concentrated liquid discharge pipeline.

[0017] Further, the bottom of the evaporation tower is also provided with a fresh air pipeline by the installed fan, when the evaporation tower is spraying, the bottom of the evaporation tower has a fresh air passing into the tower through the fan, and the air and the circulating mother liquor exchange heat and mass in the tower.

[0018] Further, the circulating mother liquor at the bottom of the evaporation tower enters the circulating mother liquor storage tank after removing the solid salt through solid-liquid separation, so as to maintain the material balance in the circulating mother liquor storage tank.

[0019] Further, the circulating water cooler is also provided with a cooling feed water pipeline and a cooling outlet water pipeline.

[0020] Further, the upper end of the water cooling tower (9) is also connected with the installed gas-liquid cyclone separator, the gas at the top of the water cooling tower removes the liquid droplets entrained therein through the gas-liquid cyclone separator, and the air discharged from the gas-liquid cyclone separator can be correspondingly sent to the fresh air pipeline to supplement fresh gas.

[0021] Beneficial effects: the present application has the following beneficial effects:

[0022] 1) the present application has the above-mentioned three circulating loops, the material loss is small, and no pollutants are generated in the treatment process, so it is a high-efficiency, clean and energy-saving down-flow double-effect evaporation method;

[0023] 2) the present application replaces the vacuum double-effect evaporator in the traditional down-flow double-effect evaporation with a heat-mass exchange evaporation tower which can operate efficiently under normal pressure, thereby avoiding the use of a vacuum system, reducing the material and working condition requirements of the equipment, and expanding the application range and field of the double-effect evaporation;

[0024] 3) the present application realizes the circulation of part of the heat energy between the evaporation tower, the water cooling tower and the circulating mother liquor primary preheater, realizes efficient recycling of waste heat, solves the problem of waste of final-effect steam heat in the known traditional down-flow double-effect evaporation, and thereby reduces the overall energy consumption of the process;

[0025] 4) the present application can completely treat the wastewater, and finally obtain crystals and purified water, wherein the organic pollutants in the purified water can be removed through subsequent elimination processes, and the purified water after subsequent treatment can be recycled as clean water;

[0026] 5) the present application can be reconstructed on the basis of the traditional down-flow double-effect evaporation process, and a small investment can bring about a substantial energy saving, and the investment recovery period is within an acceptable range; the present application has the characteristics of high efficiency, energy saving, large operation flexibility, wide water quality application range, etc., and is suitable for the comprehensive treatment of most organic matter-containing high-salinity wastewater;

[0027] 6) The ratio of the steam in the invention to the steam in the second effect is affected by the salt concentration of the wastewater itself. The higher the salt concentration of the wastewater, the more primary steam is needed to obtain secondary steam. Considering various factors, the ratio of the two should be controlled between 0.75-1.05:1. For the concentration of high-salt organic wastewater, the invention has the advantages of wide water quality adaptation range, low operating energy consumption, and avoidance of the use of a vacuum system compared to the traditional once-through double-effect evaporation. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is a structural diagram of the invention;

[0029] Figure 2 is a working principle flowchart of the invention;

[0030] Figure 3 is a coordinate graph of the amount of saturated water vapor that 1 kg of dry air can carry at different temperatures. DETAILED DESCRIPTION

[0031] The invention will be further illustrated below in conjunction with the drawings and specific examples. The examples are implemented on the premise of the technical solution of the invention and should be understood as being used to illustrate the invention rather than limit the scope of the invention.

[0032] As shown in Figure 1 and Figure 2 , a once-through double-effect evaporation concentration device for high-salt organic wastewater mainly includes three major circulation loops, wherein the evaporation tower 8, the circulating mother liquor storage tank 4, the circulating mother liquor delivery pump 5, the circulating mother liquor primary preheater 7, and the circulating mother liquor secondary preheater 6 constitute the mother liquor circulation loop; the evaporation tower 8, the water cooling tower 9, the gas-liquid cyclone separator 10, and the fan 11 constitute the gas circulation loop; the water cooling tower 9, the circulating water delivery pump 13, the circulating mother liquor primary preheater 7, and the circulating water cooler 12 constitute the water circulation loop.

[0033] Mother liquor circulation loop: the temperature of the circulating mother liquor should be between 60℃-75℃ when it enters the top of the evaporation tower 8. The evaporation loss of the circulating mother liquor in the evaporation tower 8 will be supplemented by a mixed wastewater from the wastewater delivery pump 1 in the circulating mother liquor storage tank 4, which also results in a certain increase in the salt concentration of the circulating mother liquor after each circulation, and the salt concentration of the circulating mother liquor in the storage tank will eventually reach the saturated salt concentration at the corresponding temperature. When a large amount of crystallization is needed, only the saturated circulating mother liquor in the storage tank needs to be cooled and crystallized.

[0034] Gas circulation loop: because air, nitrogen, flue gas, and other gases that are difficult to dissolve in water can carry different amounts of water vapor at different temperatures, and the higher the temperature, the more it can carry. Taking air as an example, as shown in Figure 3As shown, 1kg of 44℃ dry air can carry at most 57.7g of water vapor, while 1kg of 68℃ dry air can carry at most 195.8g of water vapor. Based on the above-mentioned physical law, the evaporation tower 8 and the water cooling tower 9 can realize the "evaporation" operation under normal pressure.

[0035] Water circulation loop: When treating high-salinity wastewater containing organic matter, some organic matter will inevitably be mixed into the hot mixed gas overflowing from the evaporation tower 8, and the organic matter will be washed down by the water in the water cooling tower 9, which will cause the accumulation of some organic matter in the circulating water. Therefore, the circulating water needs to be treated regularly to remove the accumulated organic matter, and the circulating water cooler 12 should not use direct mixing cooling but should use indirect heat exchange to avoid contamination of the coolant by the circulating water.

[0036] In the present application, the evaporation tower 8 is used to replace the conventional negative pressure two-effect evaporator of the parallel flow double-effect evaporation, thereby avoiding the negative pressure container in the process. Moreover, the water cooling tower 9 is used to recover the waste heat in the mixed gas containing saturated water vapor from the top of the evaporation tower 8, and the waste heat is used for preheating the circulating mother liquor of the evaporation tower 8, thereby saving the demand for steam from the flash tank 3 by the two-stage preheater 6 for the circulating mother liquor. The ratio of the primary steam to the secondary steam is affected by the salt concentration of the wastewater raw material, and the higher the salt concentration of the wastewater raw material, the more primary steam is needed to obtain the secondary steam. Considering various factors, the ratio of the two should be controlled within the range of 0.75-1.05:1. (Note: The primary steam here refers to the secondary steam from the flash tank 3, and the secondary steam refers to the evaporation amount of the evaporation tower 8.)

[0037] The pressures of the containers such as the flash tank 3, the circulating mother liquor storage tank 4, the evaporation tower 8, and the water cooling tower 9 are all normal pressure, thereby avoiding the use of a vacuum system; the heat source of the wastewater heater 2 is selected as low-pressure steam of 6-9 bar; and the heat load of the circulating mother liquor first-stage preheater 7 accounts for 25-35% of the total heat load of the circulating mother liquor preheater, thereby ensuring the full recovery of the waste heat in the last-stage steam.

[0038] The evaporation tower in the present application should be selected in full consideration of the properties of the evaporation medium, and a packed tower with structured packing is preferred. In order to ensure the uniform distribution of the evaporation medium on the packing, the packing should be divided into two or more sections, and each section of the packing should be equipped with a redistributor.

[0039] The water cooling tower in the present application needs to consider the same factors as the evaporation tower, and a packed tower with structured packing is also selected. The packing in the packed tower is divided into two or more sections, and each section of the packing should be equipped with a redistributor. The gas used in the evaporation tower can be air, nitrogen, flue gas, or other gases that are difficult to dissolve in water.

[0040] The technical content of the present application will be explained in detail with specific examples, and as shown in the accompanying drawings, the present application is in Figure 1 the accompanying drawings, the present application is in Figure 1 The reference signs a-k in the accompanying drawings are monitoring point signs, and the data of each monitoring point can be recorded regularly.

[0041] Example 1

[0042] In this example, the high-salinity wastewater first enters a pH neutralization and precipitation tank for pretreatment, and the pH is neutralized to 7-7.5 while removing the suspended solids therein. After pretreatment, the salt content of the wastewater is 1% (salt is NaCl), and the DMF content is 2.5%, and the wastewater is fed into the system described in the present application at a flow rate of 4571 kg / h for evaporation treatment.

[0043] The raw wastewater (4571 kg / h, 25°C) is mixed with the concentrated liquid produced by the flash tank 3 and is transported by the wastewater transport pump 1. The mixed wastewater transported by the wastewater transport pump 1 is divided into two streams, one of which (3293 kg / h, 36°C) enters the circulating mother liquor storage tank 4 for supplementing the evaporation capacity of the subsequent evaporation process; and the other stream (2106 kg / h, 36°C) is sent to the wastewater heater 2 for heating using low-pressure steam (1610 kg / h, 6 bar), and the wastewater heated to the preset temperature continues to the flash tank 3; the one-effect steam (1278 kg / h, 100°C) produced at the top of the flash tank 3 is used as the heat source for the circulating mother liquor secondary preheater 6, and the purified water condensed after heat exchange is directly sent to sewage treatment.

[0044] The circulating mother liquor transport pump 5 extracts a stream of circulating mother liquor (42757 kg / h, 44°C) from the circulating mother liquor storage tank 4 and sends it to two-stage circulating mother liquor preheaters in sequence for temperature rise, and the circulating mother liquor heated to the preset temperature (68°C) is directly sprayed from the top of the evaporation tower 8; at the same time, a stream of air (12685 kg / h, 44°C) at the bottom of the evaporation tower 8 is introduced into the tower by the fan 11, and the air and the circulating mother liquor are heat-mass transferred in the tower. The circulating mother liquor at the bottom of the evaporation tower 8 enters the circulating mother liquor storage tank 4 after removal of solid salt by the solid-liquid separator. And in order to maintain the material balance in the circulating mother liquor storage tank 4, an appropriate amount of concentrated liquid (1750 kg / h, 43°C) is continuously extracted from the storage tank.

[0045] The mixed gas (14228 kg / h, 63°C) produced from the top of the evaporation tower 8 is directly introduced into the water cooling tower 9 for cooling treatment, and the purpose of the cooling treatment is to condense the water vapor in the mixed gas. The condensed hot water stored in the tower kettle of the water cooling tower 9 is overflowed (48843 kg / h, 62°C) and then introduced into the circulating mother liquor first-stage preheater 7 through the circulating water delivery pump 13 as a heat source for heat exchange. After the heat exchange, the circulating water is divided into three streams. One stream (47300 kg / h, 55°C) is introduced into the circulating water cooler 12 and cooled to a preset temperature, and then sent to the top of the water cooling tower 9 for recycling. One stream is directly sent back to the tower kettle of the water cooling tower 9 to maintain a certain temperature. The remaining stream (1543 kg / h, 55°C) is sent to sewage treatment as purified water.

[0046] The gas at the top of the water cooling tower 9 is subjected to gas-liquid cyclone separation through the gas-liquid cyclone separator 10 to remove the liquid droplets entrained therein. The gas after removing the liquid droplets is adjusted by appropriately increasing fresh air and releasing an equal amount of gas. Finally, the gas to be recycled needs to be adjusted to be consistent with the initial indicators.

[0047] In the following table, a-j correspond to the monitoring points a-j in Figure 1 , and the following data are the data monitoring point data.

[0048] Table 1: Sample point material results

[0049]

[0050] The consumption of low-pressure steam in the conventional double-effect evaporation method is shown in the following table 2.

[0051] Table 2: Low-pressure steam consumption table

[0052]

[0053] In the conventional double-effect evaporation system, the pressure of the primary evaporator is 0.56 bar, and the pressure of the secondary evaporator is 0.13 bar. In this embodiment, both the evaporator and the evaporation tower are operated at atmospheric pressure.

[0054] The results of this embodiment show that the present application can effectively reduce the consumption of low-pressure steam by 11.8% compared with the conventional concurrent double-effect evaporation.

[0055] In this embodiment, the heat load of the circulating mother liquor multi-stage preheater is shown in the following table 3.

[0056] Table 3: Heat load of circulating mother liquor multi-stage preheater

[0057]

[0058] Compared with the current situation that the heat of the last-effect steam cannot be utilized in the traditional concurrent double-effect evaporation process, the energy-saving performance of the present application mainly lies in utilizing the heat in the water cooling tower 9 and the air at the top of the recovery evaporation tower 8, and using the heat to preheat the circulating mother liquor, that is, the greater the power of the first-stage circulating mother liquor preheater of the present application, the better the energy-saving effect in the actual working condition. In the present embodiment, the power of the first-stage circulating mother liquor preheater accounts for 32.3% of the total power of the circulating mother liquor preheater.

[0059] Embodiment 2

[0060] In the present embodiment, the high-salinity wastewater first enters the pH neutralization and precipitation tank for pretreatment, and the pH is neutralized to 7-7.5 while the suspended solids therein are removed. After the pretreatment, the wastewater has a salt content of 5% (the salt is NaCl) and a DMF content of 2.5%, and is fed into the system described in the present application at a flow rate of 4571 kg / h for evaporation treatment.

[0061] The concentrated solution produced by the flash tank 3 is mixed with the raw wastewater (4571 kg / h, 25°C) and is transported by the wastewater transport pump 1. The mixed wastewater transported by the wastewater transport pump 1 is divided into two streams, one of which (3267 kg / h, 35°C) enters the circulating mother liquor storage tank 4 and is used to supplement the evaporation amount in the subsequent evaporation process, and the other of which (2089 kg / h, 35°C) is sent to the wastewater heater 2 to be heated by using low-pressure steam (1632 kg / h, 6 bar), and the wastewater heated to the preset temperature is continuously sent to the flash tank 3. The one-effect steam (1304 kg / h) produced at the top of the flash tank 3 is used as the heat source of the second-stage circulating mother liquor preheater 6, and the purified water condensed after heat exchange is directly sent to sewage treatment.

[0062] The circulating mother liquor transport pump 5 draws a stream of circulating mother liquor (48441 kg / h, 46°C) from the circulating mother liquor storage tank 4 and sends it to the two-stage circulating mother liquor preheater for temperature rise, and the circulating mother liquor heated to the preset temperature (68°C) is directly sprayed from the top of the evaporation tower 8. At the same time, a stream of air (12685 kg / h, 44°C) at the bottom of the evaporation tower 8 is introduced into the tower by the fan 11, and the air and the circulating mother liquor are heat-mass transferred in the tower. The circulating mother liquor at the bottom of the evaporation tower 8 enters the circulating mother liquor storage tank 4 after the solid-liquid separator removes the solid salt. In order to maintain the material balance in the circulating mother liquor storage tank 4, an appropriate amount of concentrated mother liquor (1784 kg / h, 46°C) is continuously drawn from the storage tank.

[0063] The mixed gas (14169 kg / h, 64°C) produced from the top of the evaporation tower 8 is directly introduced into the water cooling tower 9 for cooling treatment, and the purpose of the cooling treatment is to condense the water vapor in the mixed gas. The condensed hot water stored in the tank of the water cooling tower 9 is overflowed (44950 kg / h, 63°C) and then introduced into the circulating mother liquor first-stage preheater 7 through the circulating water delivery pump 13 as a heat source for heat exchange. The circulating water after the heat exchange is divided into three streams, one stream (44950 kg / h, 56°C) is introduced into the circulating water cooler 12 and cooled to a preset temperature, and then sent to the top of the water cooling tower 9 for recycling; one stream is directly sent back to the tank of the water cooling tower 9 to maintain a certain temperature; and the remaining stream (1517 kg / h, 56°C) is sent to sewage treatment as purified water.

[0064] The gas at the top of the water cooling tower 9 is removed from the liquid droplets entrained therein through the gas-liquid cyclone separator 10. The gas after removing the liquid droplets is adjusted by appropriately increasing the fresh gas and releasing an equal amount of gas, and finally the indicators of the gas circulated back are consistent with those at the beginning.

[0065] The test results of this embodiment are as follows:

[0066] Table 4: Material results at sampling points

[0067]

[0068] The low-pressure steam consumption of the traditional double-effect evaporation method is shown in Table 5.

[0069] Table 5: Low-pressure steam consumption table

[0070]

[0071] The pressure of the primary evaporator of the traditional double-effect evaporation system is 0.56 bar, and the pressure of the secondary evaporator is 0.13 bar; in this embodiment, the evaporator and the evaporation tower are operated at atmospheric pressure.

[0072] The results of this embodiment show that the present application can effectively reduce the low-pressure steam consumption by 10.6% compared with the traditional concurrent double-effect evaporation.

[0073] In this embodiment, the heat load of the circulating mother liquor at each stage of the preheater is shown in Table 6.

[0074] Table 6: Heat load of circulating mother liquor at each stage of the preheater

[0075]

[0076] Compared with the current situation that the heat of the last-effect steam cannot be utilized in the traditional concurrent double-effect evaporation process, the energy-saving performance of the present application mainly lies in that the heat in the air on the top of the evaporation tower 8 is recovered by the water cooling tower 9, and the heat is used for preheating the circulating mother liquor; in the present embodiment, the power of the first-stage circulating mother liquor preheater accounts for 32.3% of the total power of the circulating mother liquor preheater.

[0077] Example 3

[0078] In the present embodiment, the high-salinity wastewater is first introduced into a pH neutralization and precipitation tank for pretreatment, so that the pH is neutralized to 7-7.5 and the suspended solids are removed. After the pretreatment, the salt content of the wastewater is 8% (the salt is NaCl), and the DMF content is 2.5%, and the wastewater is introduced into the system described in the present application at a flow rate of 4571 kg / h for evaporation treatment.

[0079] The raw wastewater (4571 kg / h, 25°C) is mixed with the concentrated solution produced by the flash tank 3 and is transported by the wastewater transport pump 1. The mixed wastewater transported by the wastewater transport pump 1 is divided into two streams, one of which (3257 kg / h, 38°C) is introduced into the circulating mother liquor storage tank 4 for supplementing the evaporation amount in the subsequent evaporation process; and the other (2359 kg / h, 38°C) is sent to the wastewater heater 2 for heating by using low-pressure steam (1659 kg / h, 6 bar), and the wastewater heated to the preset temperature is continuously sent to the flash tank 3. The one-effect steam (1314 kg / h) produced on the top of the flash tank 3 is used as the heat source of the two-stage circulating mother liquor preheater 6, and the purified water condensed after heat exchange is directly sent to sewage treatment.

[0080] The circulating mother liquor transport pump 5 draws a stream of circulating mother liquor (51837 kg / h, 47°C) from the circulating mother liquor storage tank 4 and sends it to the two-stage circulating mother liquor preheater for temperature rise, and the circulating mother liquor heated to the preset temperature (68°C) is directly sprayed from the top of the evaporation tower 8. At the same time, a stream of air (12685 kg / h, 44°C) is introduced into the tower by the fan 11, and the air and the circulating mother liquor are heat-mass transferred in the tower. The circulating mother liquor at the bottom of the evaporation tower 8 is introduced into the circulating mother liquor storage tank 4 after the solid-liquid separator removes the solid salt. In order to maintain the material balance in the circulating mother liquor storage tank 4, an appropriate amount of concentrated mother liquor (1765 kg / h, 47°C) is continuously drawn from the storage tank.

[0081] The mixed gas (14177 kg / h, 65°C) produced from the top of the evaporation tower 8 is directly introduced into the water cooling tower 9 for cooling treatment, and the purpose of the cooling treatment is to condense the water vapor in the mixed gas. The condensed hot water stored in the tank of the water cooling tower 9 is overflowed (44821 kg / h, 63°C) and then introduced into the circulating mother liquor first-stage preheater 7 through the circulating water delivery pump 13 as a heat source for heat exchange. The circulating water after the heat exchange is divided into three streams, one stream (43315 kg / h, 56°C) is introduced into the circulating water cooler 12 and cooled to a preset temperature, and then sent to the top of the water cooling tower 9 for recycling; one stream is directly sent back to the tank of the water cooling tower 9 to maintain a certain temperature; and the remaining stream (1507 kg / h, 56°C) is sent to sewage treatment as purified water.

[0082] The gas at the top of the water cooling tower 9 is removed from the liquid droplets entrained therein through the gas-liquid cyclone separator 10. The gas after removing the liquid droplets is adjusted by appropriately increasing the fresh gas and releasing an equal amount of gas, and finally the indicators of the gas circulated back are consistent with those at the beginning.

[0083] The test structure of the embodiment is as follows:

[0084] Table 7: Material results at sampling points

[0085]

[0086] The low-pressure steam consumption of the conventional double-effect evaporation method is shown in Table 8.

[0087] Table 8: List of low-pressure steam consumption

[0088]

[0089] The pressure of the primary evaporator of the conventional double-effect evaporation system is 0.56 bar, and the pressure of the secondary evaporator is 0.13 bar; the evaporator and the evaporation tower of the embodiment are operated at atmospheric pressure.

[0090] The results of the embodiment show that the invention can effectively reduce the low-pressure steam consumption by 9.3% compared with the conventional concurrent double-effect evaporation.

[0091] In the embodiment, the heat load of the circulating mother liquor at each stage of the preheater is shown in Table 9.

[0092] Table 9: List of heat loads of circulating mother liquor at each stage of the preheater

[0093]

[0094] Compared with the conventional concurrent double-effect evaporation process, the energy-saving effect of the present application is mainly embodied in the recycling of the heat in the air at the top of the evaporation tower 8 by the water cooling tower 9, and the use of the secondary heat for preheating the circulating mother liquor. That is to say, the greater the power of the primary circulating mother liquor preheater, the better the energy-saving effect in the actual working condition. In the present embodiment, the power of the primary circulating mother liquor preheater accounts for 30.8% of the total power of the circulating mother liquor preheater.

[0095] Embodiment 4

[0096] In the present embodiment, the high-salinity wastewater first enters the pH neutralization and precipitation tank for pretreatment, and the pH is neutralized to 7-7.5 while the suspended solids are removed. After pretreatment, the salt content of the wastewater is 5% (salt is NaCl), and the DMF content is 5%, and the wastewater is fed into the system at a flow rate of 4571 kg / h for evaporation treatment.

[0097] The concentrated solution produced by the flash tank 3 is mixed with the raw wastewater (4571 kg / h, 25°C) and transported by the wastewater delivery pump 1. The mixed wastewater delivered by the wastewater delivery pump 1 is divided into two streams, one of which (3260 kg / h, 35°C) enters the circulating mother liquor storage tank 4 for supplementing the evaporation amount in the subsequent evaporation process, and the other (2085 kg / h, 35°C) is sent to the wastewater heater 2 for heating by low-pressure steam (1614 kg / h, 6 bar). The wastewater heated to the preset temperature continues to pass through the flash tank 3. The primary steam (1311 kg / h) produced at the top of the flash tank 3 is used as the heat source for the secondary circulating mother liquor preheater 6, and the purified water condensed after heat exchange is directly sent to the sewage treatment.

[0098] The circulating mother liquor delivery pump 5 draws a stream of circulating mother liquor (50687 kg / h, 46°C) from the circulating mother liquor storage tank 4 and sends it to the two-stage circulating mother liquor preheater for warming. The circulating mother liquor warmed to the preset temperature (68°C) is directly sprayed from the top of the evaporation tower 8. At the same time, a stream of air (12685 kg / h, 44°C) at the bottom of the evaporation tower 8 is introduced into the tower by the fan 11, and the air and the circulating mother liquor are heat-mass transferred in the tower. The circulating mother liquor at the bottom of the evaporation tower 8 enters the circulating mother liquor storage tank 4 after the solid-liquid separator removes the solid salt. In order to maintain the material balance in the circulating mother liquor storage tank 4, an appropriate amount of concentrated mother liquor (1774 kg / h, 52°C) is continuously drawn from the tank.

[0099] The mixed gas (14171 kg / h, 64°C) produced from the top of the evaporation tower 8 is directly introduced into the water cooling tower 9 for cooling treatment, and the purpose of the cooling treatment is to condense the water vapor in the mixed gas. The condensed hot water stored in the tank of the water cooling tower 9 is overflowed (44586 kg / h, 63°C) and then introduced into the circulating mother liquor first-stage preheater 7 through the circulating water delivery pump 13 as a heat source for heat exchange. The circulating water after the heat exchange is divided into three streams, one stream (43076 kg / h, 56°C) is introduced into the circulating water cooler 12 and cooled to a preset temperature, and then sent to the top of the water cooling tower 9 for recycling; one stream is directly sent back to the tank of the water cooling tower 9 to maintain a certain temperature; and the remaining stream (1510 kg / h, 56°C) is sent to the sewage treatment as purified water.

[0100] The gas at the top of the water cooling tower 9 is removed from the liquid droplets entrained therein through the gas-liquid cyclone separator 10. The gas after removing the liquid droplets is adjusted by appropriately increasing the fresh gas and releasing an equal amount of gas, and finally the indicators of the gas circulated back are consistent with those at the beginning.

[0101] The results of the example are as follows:

[0102] Table 10: Material results at sampling points

[0103]

[0104] The consumption of low-pressure steam in the traditional double-effect evaporation method is shown in Table 11.

[0105] Table 11: Low-pressure steam consumption table

[0106]

[0107] The pressure of the primary evaporator in the traditional double-effect evaporation system is 0.56 bar, and the pressure of the secondary evaporator is 0.13 bar; the evaporator and the evaporation tower in the example are operated at atmospheric pressure.

[0108] The results of the example show that the application can effectively reduce the consumption of low-pressure steam by 10.3% compared with the traditional concurrent double-effect evaporation.

[0109] In the example, the heat load of the circulating mother liquor at each stage of the preheater is shown in Table 12.

[0110] Table 12: Heat load of circulating mother liquor at each stage of the preheater

[0111]

[0112] Compared with the current situation that the heat of the last-effect steam cannot be utilized in the traditional concurrent double-effect evaporation process, the energy-saving performance of the present application mainly lies in that the heat in the air on the top of the evaporation tower 8 is recovered by the water cooling tower 9, and the secondary heat is used for preheating the circulating mother liquor. That is to say, the greater the power of the primary circulating mother liquor preheater of the present application, the better the energy-saving effect of the actual working condition. In the present embodiment, the power of the primary circulating mother liquor preheater accounts for 32.1% of the total power of the circulating mother liquor preheater.

[0113] Example 5

[0114] In the present embodiment, the high-salinity wastewater first enters the pH neutralization and precipitation tank for pretreatment, and the pH is neutralized to 7-7.5 while the suspended solids therein are removed. After the pretreatment, the salt content of the wastewater is 5% (the salt is NaCl), and the EtOH content is 2.5%. The wastewater is fed into the system described in the present application at a flow rate of 4571 kg / h for evaporation treatment.

[0115] The concentrated liquid produced by the flash tank 3 is mixed with the raw wastewater (4571 kg / h, 25°C) and transported by the wastewater delivery pump 1. The mixed wastewater delivered by the wastewater delivery pump 1 is divided into two streams, one of which (3350 kg / h, 37°C) enters the circulating mother liquor storage tank 4 for supplementing the evaporation amount in the subsequent evaporation process, and the other (2142 kg / h, 37°C) is sent to the wastewater heater 2 for heating by using low-pressure steam (1534 kg / h, 6 bar). After being heated to the preset temperature, the wastewater continues to pass through the flash tank 3. The one-effect steam (1221 kg / h) produced on the top of the flash tank 3 is used as the heat source of the secondary circulating mother liquor preheater 6, and the purified water condensed after heat exchange is directly sent to the sewage treatment.

[0116] The circulating mother liquor delivery pump 5 draws a stream of circulating mother liquor (42029 kg / h, 43°C) from the circulating mother liquor storage tank 4 and sends it to two circulating mother liquor preheaters for temperature rise. The circulating mother liquor heated to the preset temperature (68°C) is directly sprayed from the top of the evaporation tower 8. At the same time, a stream of air (12685 kg / h, 44°C) at the bottom of the evaporation tower 8 is introduced into the tower by the fan 11, and the air and the circulating mother liquor are heat-mass transferred in the tower. The circulating mother liquor at the bottom of the evaporation tower 8 enters the circulating mother liquor storage tank 4 after the solid-liquid separator removes the solid salt. In order to maintain the material balance in the circulating mother liquor storage tank 4, an appropriate amount of concentrated mother liquor (1559 kg / h, 43°C) is continuously drawn from the storage tank.

[0117] The mixed gas (14476 kg / h, 62℃) produced from the top of the evaporation tower 8 is directly introduced into the water cooling tower 9 for cooling treatment, and the purpose of the cooling treatment is to condense the water vapor in the mixed gas. The condensed hot water stored in the tank of the water cooling tower 9 is overflowed (52860 kg / h, 61℃) and then introduced into the circulating mother liquor first-stage preheater 7 through the circulating water delivery pump 13 as a heat source for heat exchange. The circulating water after the heat exchange is divided into three streams, one stream (51175 kg / h, 54℃) is introduced into the circulating water cooler 12 and cooled to a preset temperature, and then sent to the top of the water cooling tower 9 for recycling; one stream is directly sent back to the tank of the water cooling tower 9 to maintain a certain temperature; and the remaining stream (1685 kg / h, 54℃) is sent to the sewage treatment as purified water.

[0118] The gas at the top of the water cooling tower 9 is removed from the liquid droplets entrained therein through the gas-liquid cyclone separator 10. The gas after removing the liquid droplets is adjusted by appropriately increasing the fresh gas and releasing an equal amount of gas, and finally the indicators of the gas circulated back are consistent with those at the beginning.

[0119] The test results of this embodiment are as follows:

[0120] Table 13: Material results at sampling points

[0121]

[0122] The consumption of low-pressure steam in the traditional double-effect evaporation method is shown in the following table 14.

[0123] Table 14: Low-pressure steam consumption table

[0124]

[0125] The pressure of the primary evaporator in the traditional double-effect evaporation system is 0.56 bar, and the pressure of the secondary evaporator is 0.13 bar; the evaporator and the evaporation tower in this embodiment are operated at atmospheric pressure.

[0126] The results of this embodiment show that the present application can effectively reduce the consumption of low-pressure steam by 17.8% compared with the traditional counterflow double-effect evaporation.

[0127] In this embodiment, the heat load of the circulating mother liquor at each stage of the preheater is shown in the following table 15.

[0128] Table 15: Heat load of circulating mother liquor at each stage of the preheater

[0129]

[0130] Compared with the current situation that the heat of the last-effect steam cannot be utilized in the traditional concurrent double-effect evaporation process, the energy-saving performance of the present application mainly lies in that the heat in the air on the top of the evaporation tower 8 is recovered by the water cooling tower 9, and the secondary heat is used for preheating the circulating mother liquor. That is to say, the greater the power of the primary circulating mother liquor preheater of the present application, the better the energy-saving effect of the actual working condition. In the present embodiment, the power of the primary circulating mother liquor preheater accounts for 33.7% of the total power of the circulating mother liquor preheater.

[0131] Example 6

[0132] In the present embodiment, the high-salinity wastewater first enters the pH neutralization and precipitation tank for pretreatment, and the pH is neutralized to 7-7.5 while the suspended solids therein are removed. After the pretreatment, the wastewater has a salt content of 5% (the salt is NaCl), an EtOH content of 2.5%, and a DMF content of 2.5%, and is fed into the system described in the present application at a flow rate of 4571 kg / h for evaporation treatment.

[0133] The concentrated solution produced by the flash tank 3 is mixed with the raw wastewater (4571 kg / h, 25°C) and is transported by the wastewater transport pump 1. The mixed wastewater transported by the wastewater transport pump 1 is divided into two streams, one of which (3349 kg / h, 38°C) enters the circulating mother liquor storage tank 4 and is used to supplement the evaporation amount in the subsequent evaporation process, and the other of which (2233 kg / h, 38°C) is sent to the wastewater heater 2 to be heated by using low-pressure steam (1514 kg / h, 6 bar), and the wastewater heated to the preset temperature is continuously sent to the flash tank 3. The one-effect steam (1220 kg / h) produced on the top of the flash tank 3 is used as the heat source of the secondary circulating mother liquor preheater 6, and the purified water condensed after heat exchange is directly sent to sewage treatment.

[0134] The circulating mother liquor transport pump 5 extracts a stream of circulating mother liquor (40481 kg / h, 43°C) from the circulating mother liquor storage tank 4 and sends it into the two circulating mother liquor preheaters in sequence for temperature rise. The circulating mother liquor heated to the preset temperature (68°C) is directly sprayed from the top of the evaporation tower 8. At the same time, a stream of air (12685 kg / h, 44°C) is introduced into the tower by the fan 11, and the air and the circulating mother liquor exchange heat and mass in the tower. The circulating mother liquor at the bottom of the evaporation tower 8 enters the circulating mother liquor storage tank 4 after the solid-liquid separator removes the solid salt. In order to maintain the material balance in the circulating mother liquor storage tank 4, an appropriate amount of concentrated mother liquor (1612 kg / h, 43°C) is continuously extracted from the storage tank.

[0135] The mixed gas (14422 kg / h, 61℃) produced from the top of the evaporation tower 8 is directly introduced into the water cooling tower 9 for cooling treatment, and the purpose of the cooling treatment is to condense the water vapor in the mixed gas. The condensed hot water stored in the tank of the water cooling tower 9 is overflowed (39404 kg / h, 61℃) and then introduced into the circulating mother liquor first-stage preheater 7 through the circulating water delivery pump 13 as a heat source for heat exchange. The circulating water after the heat exchange is divided into three streams, one stream (37718 kg / h, 51℃) is introduced into the circulating water cooler 12 and cooled to a preset temperature, and then sent to the top of the water cooling tower 9 for recycling; one stream is directly sent back to the tank of the water cooling tower 9 to maintain a certain temperature; and the remaining stream (1686 kg / h, 51℃) is sent to the sewage treatment as purified water.

[0136] The gas at the top of the water cooling tower 9 is removed from the liquid droplets entrained therein through the gas-liquid cyclone separator 10. The gas after removing the liquid droplets is adjusted by appropriately increasing the fresh gas and releasing an equal amount of gas, and finally the indicators of the gas circulated back are consistent with those at the beginning.

[0137] The test results of this embodiment are as follows:

[0138] Table 16: Material results at sampling points

[0139]

[0140] The consumption of low-pressure steam in this embodiment and the conventional double-effect evaporation method is shown in Table 17 as follows.

[0141] Table 17: Consumption list of low-pressure steam

[0142]

[0143] The pressure of the primary evaporator in the conventional double-effect evaporation system is 0.56 bar, and the pressure of the secondary evaporator is 0.13 bar; the evaporator and the evaporation tower in this embodiment are operated at atmospheric pressure.

[0144] The results of this embodiment show that the present application can effectively reduce the consumption of low-pressure steam by 17.5% compared with the conventional concurrent double-effect evaporation.

[0145] In this embodiment, the heat load of the circulating mother liquor at each stage of the preheater is shown in Table 18 as follows.

[0146] Table 18: Heat load list of circulating mother liquor at each stage of the preheater

[0147]

[0148] Compared with the current situation that the heat of the last-effect steam cannot be utilized in the conventional concurrent double-effect evaporation process, the energy-saving performance of the present application mainly lies in that the heat in the air on the top of the evaporation tower 8 is recovered by the water cooling tower 9, and the secondary heat is used to preheat the circulating mother liquor. That is to say, the greater the power of the first-stage circulating mother liquor preheater of the present application, the better the energy-saving effect of the actual working condition. In the present embodiment, the power of the first-stage circulating mother liquor preheater accounts for 32.1% of the total power of the circulating mother liquor preheater.

[0149] The following is the comparison of the above six embodiments as shown in Table 19:

[0150] Table 19 Comparison of each embodiment

[0151]

[0152] In the above table, the energy-saving performance of the present application = the power of the first-stage circulating mother liquor preheater / the total power of the circulating mother liquor preheater; the expected energy-saving performance = (the unit consumption of low-pressure steam of the conventional double-effect evaporation - the unit consumption of low-pressure steam of the present application) / the unit consumption of low-pressure steam of the conventional double-effect evaporation.

[0153] From the above embodiments, it can be concluded that compared with the conventional concurrent double-effect evaporation (two single-effect evaporations are connected in series, and the heat of the second-effect evaporation is derived from the steam generated by the first-effect evaporation), the present application has the advantages of wide water quality adaptation range, low running energy consumption, and avoidance of the use of a vacuum system, etc.

[0154] The above specific embodiments are only a preferred embodiment of the present application, and are not intended to limit the implementation and the scope of claims of the present application. Any equivalent changes and modifications made in accordance with the content of the patent protection scope of the present application should be included in the scope of the patent application of the present application.

Claims

1. A co-current double-effect evaporation and concentration device for high-salt organic wastewater, characterized in that: It includes a wastewater transfer pump (1), a wastewater heater (2), a flash tank (3), a circulating mother liquor storage tank (4), a circulating mother liquor transfer pump (5), a primary circulating mother liquor preheater (7), a secondary circulating mother liquor preheater (6), an evaporator (8), and a water cooling tower (9). The concentrated liquid generated in the flash tank (3) is discharged from the bottom and transported together with the wastewater collected by the wastewater pipeline via the wastewater transfer pump (1). The mixed wastewater transported by the wastewater transfer pump (1) is divided into two streams, one of which enters the circulating mother liquor storage tank (4) to supplement the evaporation volume of the subsequent evaporation process. Another stream of wastewater is sent to the wastewater heater (2) for heating. After being heated to the preset temperature, the wastewater is sent to the flash tank (3). The top of the flash tank (3) generates a single-effect steam. The single-effect steam is sent to the secondary preheater (6) of the circulating mother liquor as the heat source of the secondary preheater (6). After heat exchange and condensation in the secondary preheater (6), purified water is discharged and sent to the sewage treatment plant. The circulating mother liquor transfer pump (5) draws a stream of circulating mother liquor from the circulating mother liquor storage tank (4) and sends it sequentially to the circulating mother liquor primary preheater (7) and the circulating mother liquor secondary preheater (6) for heating. After the temperature is raised to the preset temperature, the circulating mother liquor is sent to the evaporation tower (8) for spraying. The mixed gas generated in the evaporation tower (8) is sent to the water cooling tower (9) for cooling treatment, and the water vapor in the mixed gas is condensed. It also includes a circulating water transfer pump (13) and a circulating water cooler (12); after the condensed hot water stored in the water cooling tower (9) overflows, it is sent to the circulating mother liquor primary preheater (7) by the set circulating water transfer pump (13) for heat exchange, and the circulating water after heat exchange is divided into three streams. One stream is sent to the circulating water cooler (12) to be cooled to the preset temperature and then sent to the water cooling tower (9) for recycling; one stream is sent directly back to the water cooling tower (9) to maintain the tower bottom temperature; and the last stream is sent to the sewage treatment as purified water. The wastewater heater (2) heats the wastewater entering it by sending in low-pressure steam, and discharges steam condensate after heating; the circulating mother liquor storage tank (4) is also equipped with a concentrated liquid discharge pipe; the bottom of the evaporator (8) is also equipped with a fresh air pipe through the installed fan (11). When the evaporator (8) is spraying, a stream of fresh air is introduced into the tower through the fan (11) from the bottom of the evaporator (8). This stream of air and the circulating mother liquor undergo heat and mass transfer in the tower.

2. The co-current double-effect evaporation and concentration device for high-salt organic wastewater according to claim 1, characterized in that: After solid salts are removed by solid-liquid separation, the circulating mother liquor at the bottom of the evaporation tower (8) enters the circulating mother liquor storage tank (4) to maintain the material balance in the circulating mother liquor storage tank (4).

3. The co-current double-effect evaporation and concentration device for high-salt organic wastewater according to claim 1, characterized in that: The circulating water cooler (12) is also equipped with a cooling water supply pipe and a cooling water outlet pipe.

4. The co-current double-effect evaporation and concentration device for high-salt organic wastewater according to claim 1, characterized in that: The upper end of the water cooling tower (9) is also connected to a gas-liquid cyclone separator (10). The gas at the top of the water cooling tower (9) is de-entrained by the gas-liquid cyclone separator (10); and the air discharged from the gas-liquid cyclone separator (10) is sent to the fresh air duct to replenish fresh gas.

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